Assembly line production of assembled systems requires that the process elements comprising the assembled systems be interchangable. That is, for instance, if process elements "X" and "Y" are designed to be interconnected in an assembled system, any of a multiplicity of process elements "X" must be interconnectable to, with or in etc. any of a multiplicity of process elements "Y". The interchangeability of process elements is the basis of the economy of the assembly/positioning line approach to manufacturing and also makes field maintenance of assembled systems relatively easy. It is a fact of any manufacturing process, however, that process elements can not be manufactured to absolutely exact design dimensions. That is, tolerances in corresponding dimensions in a multiplicity of said process elements will exist. The presence of tolerances in process elements, it should be appreciated, can not be avoided and said tolerances are the cause of many problems during the process of assembling said tolerance dimensioned process elements into systems. Engineers are constantly concerned with the overall quality, form, fit and function of system process elements and assembled systems, and are guided toward achieving desired results by a system termed "tolerancing". Put simply, manufactured system process elements are deemed acceptable when their dimensions fall within a specified range.
It should be understood that there are basically three goals associated with the assembly or positioning of process elements. These goals can be demonstrated using toleranced length first process element and toleranced depth holes in second process elements as examples. The first goal is that toleranced length first process elements should be safely, repeatably, precisely and consistantly positionable with respect to, and/or inserted into, toleranced depth holes in second process elements. Second, precise control of gauging force between abutted ends of toleranced length first process elements and second process elements should be possible. (Note that the term "gauging force" refers to the force present between two process elements at their abutted point(s) of contact, when said process elements are assembled into a system. It is the result of the pressure of contact over the area of said abuttment between said process elements). The third goal is that goals one an two should be achievable regardless of variations in lengths, depths and outer and inner dimensions of toleranced length first process elements and toleranced depth holes in second process element. That is, sufficient "insertional forces" must be available and gauging forces should be controllable independently of required insertional forces. (It is noted that "insertional" forces are those required to force one process element into a system with a second process element).
One acceptable approach under the system of tolerancing is to require that tolerances in the process elements involved be kept very tight, (i.e.. small). Such "over-tolerancing" in the manufacturing process typically involves quality control selection of acceptably dimensioned process elements and rejection of process elements which emerge from the manufacturing process "out-of-tolerance". As a result a large amount of waste is involved, both in man-hours and in materials, when this approach is adopted, and the costs involved can quickly become prohibitive.
Another approach to overcomming the problems involved in the assembly and/or positioning of tolerance dimensioned process elements into systems or with respect to one another is to utilize machines which facilitate the assembly and/or positioning process such that larger tolerances in process element dimensions become acceptable. Machines utilized under this approach typically fall into one of two categories.
The first category is that demonstrated by fixed stroke length machines which provide a variable process element "gauging force", such as fixed "shut height" gauging force uncompensated presses. (Note the term "shut height" refers to the minimum distance achieved between the end of a stroking piston and a fixed base during a stroking cycle and is typically set by a user). As the name implies, these machines cycle a fixed displacement every stroke. A typical machine of this type is commonly known as a "punch press". A punch press typically comprises a rigid frame formed to resemble the letter "C". The upper portion of the said frame is configured to provide a sliding means in which a "ram" or "piston" is slideably fitted so that it can travel perpendicular to the lower portion of the rigid frame, which can be termed the "base". It is noted that process elements are placed upon said base during use and said ram or piston can be operated to apply force to said process elements when so located. The ram or piston is connected to a crankshaft via an adjustable "connecting rod" which typically is also connected to an energy storing flywheel which, in turn, is typically powered by an electric motor. The capacity of the fixed stroke length machine is determined by the flywheel/connecting rod combination in combination with the stroke length. As alluded to, fixed stroke length machines typically fix the location of the base with respect to the fixed stroke length piston and do not provide any force absorbing capability in either the base or piston systems thereof. That is, during a cycle of use, when the crankshaft is at bottom-dead-center (BDC), and the lower end of a ram or piston is at its shut height above said base, a low tolerance dimensioned process element present on said base can be subjected to a user determined force. Tolerances in the height of a process element, and in machine elements, however, which result from stresses or temperature changes for instance, can pose a real problems and it should be appreciated that careful adjustment of the shut height is required to accomodate worst case tolerances. Fixed stroke length machines are particularly relevant to assembly processes in which "insertional" forces are required and/or in which a fixed displacement stroke length is otherwise acceptable or required, but in which careful control of "gauging" forces between assembled system elements is not required. Fixed stroke length machines are particularly applicable, but not limited to use in the assembly of relatively strong and rugged tolerance dimensioned process elements, which assembly requires development of an insertional force sufficient to effectively overcome "insertional resistance". Insertional resistance exists, for instance, where a first process element outer dimension is not sufficiently smaller than the inner dimension of a hole in a second process element into which said first process element is to be inserted, to allow an essentially frictionless gravity feed insertion. The result of simply providing sufficient insertional force to said process elements to assemble them into a system is typically termed a "press-fit". While a press fit is sufficient in many situations, it must then be understood that the gauging force between the inserted end of a toleranced length first process element and the end of a toleranced depth hole in a second process element into which the toleranced length first process element is inserted can not be accurately controlled by a fixed stroke length machine, emphasis added. In that light it should be appreciated that in many cases fixed stroke length machines do not provide sufficient means for compensating for tolerances in lengths of process elements assembled therein, nor it is mentioned, do they provide means for compensating for tolerances which result from stresses developed during use in elements of the fixed stroke length machine per se. it is specifically noted that when tolerance dimensioned process elements to be assembled are relatively delicate and/or gauging forces between assembled tolerance dimensioned process elements are to be carefully controlled, use of a fixed stroke length machine without tolerance compensation capability is generally contra-indicated. It should also be appreciated that fixed stroke length machines can be dangerous to operate. For instance, a fixed stroke length machine configured to apply "X" tons of force at the end of a stroking piston, at a shut height above a fixed base on the order of a fraction of an inch, and which fixed stroke length provides space between said fixed base and said end of said stroking piston in said fixed stroke length machine at other times during a stroke cycle operation sufficient for an operator's hand to be inserted thereinto, can lead to serious operator injury. Additionally, placing a relatively noncompressable process element on said fixed base which is of a dimension larger than the effective shut height of a fixed stroke length machine can cause elements internal to a fixed stroke length machine to become stressed to the point of breaking in a violent manner when said process elementals subjected to pressing force by said fixed stroke length machine. In such a situation a fixed base might break, the fixed stroke piston might break or an energy containing rotating flywheel present in said fixed stroke length machine might snap free of an attaching shaft. As well, associated tooling and process elements can be damaged. Again, serious injury to an operator or to adjacent equipment etc. is a real possibility if fixed stroke machines are not carefully controlled by experienced personnel. It should also be noted that a fixed stroke length machine which does not include means for tolerance compensation of internal elements can incidiously, as a result of, for instance, thermal expansion of internal elements during use, become dangerous to operate without a user thereof making any adjustments thereto or otherwise suspecting a problem is developing.
The second category of machine is that demonstrated by variable stroke length machines which can provide variable tolerance dimensioned process element gauging pressures between abutted surfaces of process elements assembled therein during use. Variable stroke length machines can be envisioned as generally similar to fixed stroke length machines but in which, for instance, the base upon which a process element is positioned during use can move during use and thereby absorb some of the force applied to a tolerance dimension process element placed thereon, by a stroke piston. Force absorbing elements can also, or in the alternative, be placed in a stroking piston system of such variable stroke length machines. Machines in this category utilizing hydraulic or pneumatic cylinder type force absorbing means typically enable achieving an intended tolerance process element abutted surface gauging force, (which is the difference between applied force and required insertional force), even when a press-fit insertional force is required, but those utilizing "springs" typically enable effecting an intended tolerance process element gauging force between assembled process elements only when press-fit insertional force is relatively small. Hydraulic or pneumatic cylinder utilizing variable stroke length machines are capable of providing a fixed force over a relatively large stroke length, whereas spring utilizing variable stroke length machines provide a variable force over an effective stroke length. It is also noted that the piston in a varaible stroke length machine should never reach the end of its stroke during use, as a fixed stroke length configuration is then effected. Variable stroke length machines are particularly relevant to assembly or positioning of relatively delicate tolerance dimensioned process elements to which large forces can not be applied without ruining said tolerance dimensioned process elements, and/or in which a variable stroke length is otherwise appropriate to properly interconnect relevant tolerance dimensioned process elements. That is, such machines are particularly indicated when large tolerance dimensioned process element insertional forces are not required, or even tolerable, during an assembly or positioning process, but for instance, when relatively better control of assembled tolerance dimensioned process element gauging forces is required. (Note that when hydraulic or pneumatic cylinder type utilizing variable stroke machines are used a relatively large insertional force can also be simultaneously provided). Variable stroke length machines are, within limits, somewhat safer to operate than fixed stroke machines because of the force absorbing elements present therein, but they can still cause serious damage and/or injury when the limits of the force absorbing elements are exceeded. In addition typical variable stroke length machines are unable to fully compensate for tolerances which develop in internal elements thereof during use because of, for instance, heating or element stressing. As well, it is typically necessary to design custom variable stroke length machines for specific intended purposes. In this respect they are not superior to fixed stroke machines.
It should be appearant that operators of both fixed and variable length machines must have a thorough understanding of said machines and must have capabilities far in excess of those which allow the following of a fixed set of non-varying instructional steps.
An appropriate example to better clarify the foregoing is that involving the process of inserting of a toleranced length first process element into a mated toleranced depth hole in second process element, to form an assembled system. The goal of the process being that the end of toleranced length first process element inserted into the mated toleranced depth, (typically flat bottomed), hole in the second process element, be placed precisely and intimately in abutted contact with the end of said toleranced depth hole with an intended gauging force present at the point of contact. If the tolerances of the identified system process elements are such that the outer diameter, (assuming circular shaped toleranced length first process element and toleranced depth hole in said second process element), of the toleranced length first process element is always smaller than the inner diameter of the toleranced depth hole in the second process element, simple gravity feed might be sufficient to properly position said process elements with respect to one another and machine requirments would be reduced to positioning and transfering means. As well, a variable stroke machine utilizing springs might be utilized. If the tolerances of the outer diameter of the toleranced length first process element and the inner diameter of the toleranced depth hole in the second process element are such that an insertional force is required to cause the identified insertion, the first class of machine above, or a machine from the second class which utilizes hydraulic or pneumatic cylinders or strong springs would probably be indicated to cause a "press-fit". However, tolerances in the length of the first process element, and the depth of the hole in the second process element will not always be accommodated by the relatively fixed stroke length provided by either of said machines, and precise control of the gauging force between abutted surfaces of the assembled tolerance process elements will not repeatably and consistently result.
From the above it should be appearant that a fixed stroke length machine, with the capability of providing sufficiently large insertional forces to overcome tolerances in the relative diameters of first and second process elements as described above, but which would simultaneously independently effect precise and repeatable control of gauging force between assembled abutted ends of toleranced length first process elements and the ends of toleranced depth holes in second process elements when insertional forces are required, would be of great utility. However, even were a fixed stroke length machine, such as those described above, available which provided the identified superior attributes, (which it is not), as valuable as it would be, problems would still exist in that tolerances which occur in internal elements thereof would not be adequately compensated. As mentioned above such tolerances can result from stresses which develop during use, and from, for instance, the effect of thermal expansion etc. It should further be appreciated at this point, that a system which would simultaneously overcome all said identified problems and which would allow a user thereof to safely follow a set method of use without the requirement that a "feel" be relied upon to arrive at consistent repeatable optimum results would be of great utility.
A particularly relevant, but by no means limiting, use for such a machine would be to facilitate the safe, precise, repeatable and consistent loading of essentially cylindrical shaped toleranced diameter and length primers into essentially cylindrical shaped toleranced diameter and depth flat bottomed primer pocket holes in bullet shell casings in a manner which would not damage said primers or bullet shell casings and which would allow precise control of the gauging force between assembled primer and bullet shell casing systems while providing the insertional force required to form the assembled system. It has long been known that proper insertion of primers into mating bullet shell casing pockets can improve the flight of bullets fired therefrom. In cases wherein the primer is seated "short", (i.e. the primer anvil does not touch or make intimate contact with the bottom of its mating pocket in the cartridge case), a situation presents wherein lock-times are increased, (i.e. the total time it takes from the moment the trigger releases the firing pin until the detonation of the primer occurs). This results as the firing pin must drive the primer to its seat before enough energy can be exerted to cause detonation. This produces a "cushioning" effect which robs some of the available energy from the firing pin and reduces its effectiveness. In cases wherein the primer is seated "long", (i.e. seated too deep), a situation occurs where the primer anvil is forced into the explosive element of the primer causing it to crack or break up. Both situations can cause erratic ignitions of the primer and adversly effect the burning characteristics of the powder, and hence, the overall accuracy of a bullets flight due to changes in velocity. A search of the prior art in this area has shown that the problems associated with tolerances during assembly of primers and bullet cartridges has not been solved.
U.S. Pat. No. 5,025,706 to markle is perhaps the most relevant and describes a manually operated controlled depth primer seating tool and a multi-step method of use thereof. The Markle invention makes a significant step toward a solution to the problems identified above but falls short of meeting all of the identified criteria. While tolerances in both the depth of the primer pocket in a center fire cartridge and in the length of a primer inserted thereinto are meant to be compensated when a user follows a described method of use of said invention system, he or she must be capable of reading and setting a dial on a gauge when the system is configured with a primer entered to one portion of the invention system, and then said primer must be removed and placed into another portion of the invention system to allow its insertion into a primer pocket in a center fire cartridge. The required repeated handling of the primer is undesirable as it can lead to contamination thereof with body oils etc. Said contamination can lead to primer misfiring in use. In addition, the method of use of the invention requires that a user apply "overseating" forces, but provides no means by which a user can determine how much of said overseating force is necessary because of internal system tolerances which develop because of application of said overseating force, and how much of said overseating force actually appears as gauging force between assembled primers and cartridge primer seats. In addition, no means of compensating internal system tolerances is present. While it appears that the Markle invention works better than other inventions, (discussed directly), intended for similar purposes, and provides an advancement in the art, to practice the method of use described requires that a user be capable of taking readings from a dial, setting said dial, repeatably handle primers and cartridge cases and apply overseating forces which, in part, are necessary to overcome internal system tolerances. That is, a user can not simply follow a set procedure and consistently and repeatably arrive at optimum results, and the ability of a user appears to play heavily in successful use of the Markle invention system, as is the case regarding systems and methods found in other Patents. A system and method of use which would overcome the identified problems is therefore still needed.
U.S. Pat. No. 4,522,102 to Pickens describes a system which allows a user to tend to automatically remove spent primers from cartridges, admit powder into cartridges, introduce and insert bullets into cartridges, crimp and seal said bullets into said cartridges and insert and introduce new primers into said cartridges. The primer insertion portion of the system appears to utilize a variable length stroke non-spring compensated approach to properly mate said primer into said cartridge. This requires a user controlled "feel" over the gauging force between a cartridge primer pocket and a primer inserted thereinto.
U.S. Pat. No. 3,313,201 to Lawrence describes a fixed stroke length system for inserting primers into a cartridge case which uses the face of a cartridge to act as a gauging point of reference, thereby compensating for tolerances in rim depths. However, shrinkage in the primer compounds and tolerances in the lengths of primers and of cartridge pockets are not compensated, and no means by which a user can control gauging force are present.
U.S. Pat. No. 3,636,812 to Nuler describes a tool system which allows adjustment of the depth a fixed stroke length punch system will insert a primer into primer pocket of a cartridge case. The tool system is hand held and operated by a user by an action consisting of squeezing a handle toward the body of the tool system. Said user action causes, via a linkage mechanism, a primer to be pressed into said primer pocket. Said tool system provides a fixed stroke length but provides an adjustment to the shut height which allows achieving an effective variable stroke length result. It is not clear, however, how a user will know how to perform said adjustment to achieve an optimum end result without measuring each primer length and primer pocket depth individually. Again means by which a user can adjust gauging force are not present.
United Kingdom Patent No. GB 2,188,130 to Hans describes another system for seating primers into cartridge cases which appears to utilize a fixed stroke system approach which also provides an adjustment to the shut height which allows achieving an effective variable stroke length result. It is again unclear how a user will know how to set the device to achieve an optimum end result, as noted with respect to the Nuler invention. Again, means by which a user can adjust gauging force are not present.
Finally, U.S. Pat. No. 4,289,258 to Ransom describes a safety charge measuring device for cartridge loading machines. Said system includes a sliding charge receiver which allows positioning a charge receiving hole therein under a powder receiving hole to allow loading powder thereinto, and which also allows subsequent positioning of said powder loaded charge receiving hole over powder feed chute to deliver it into a bullet cartridge.
It should, in view of the foregoing, be appreciated that the precise loading of toleranced length first process elements, (such as primers), into toleranced depth holes in second process elements, (such as primer pockets in bullet shell casings), presents a difficult problem. While various inventors have struggled with the problem and provided various systems and methods of use aimed at solving it, a need still exists for a system and method of use which allows a user, with no other ability than to follow a set sequence of invariant steps, and without the need to develop and rely on a "feel", to safely, repeatably and consistently insert toleranced length first process elements into toleranced depth holes in second process such that a precise and intimate intended assembled system is easily and repeatably achieved with an intended gauging force present between abutted ends of said assembled elements. Such system and method should provide for development of sufficient insertional force consistent with completely independent control of an end point gauging force present between assembled process elements at their point of contact. In addition there should be no requirement of removal of a toleranced length first process element from said system after entered thereto, until it is precisely loaded into a toleranced depth hole in a second process element. Said system and method of use should automatically provide for compensation of tolerances in toleranced length first process elements and in toleranced depth holes in second process elements, as well as in internal system elements, (such as those resulting from stresses on internal system elements during use and thermal expansion etc.), without the need that a user read and set dials etc. or do anything other than follow a set sequence of definite steps. In addition, the system should be safe to use and should allow multiple such systems to be simultaneously used and controlled from a single control system without adverse interaction therebetween, even when greatly differing size process elements are being processed by different of said multiple systems and even if two process elements are not coplanar with each other. Such a system should allow simplification of quality control and manufacturing processes, eliminate waste, reduce manufacturing set-up times, provide higher quality assembled goods, save money by allowing use of large tolerance process elements and eliminate any need to pre-gauge or sort tolerance parts. In addition, such a system should be applicable to use in positioning process elements with respect to one another when insertion of one into another is not required to form a system, or when positioning of one process element to allow processing thereof is to be achieved.
The present invention meets the identified need.